Inhibition of phosphatase activity as a novel treatment for chronic toxoplasmosis

描述（由申请方提供）：本申请涉及由原生动物寄生虫弓形虫引起的潜伏性慢性感染。在宿主体内，弓形虫从引起急性感染的增殖期（速殖子）转变为潜伏性包囊期（缓殖子），从而建立终身慢性感染。慢性弓形虫病具有重要的临床意义，因为潜伏感染可以重新激活为危及生命的急性弓形虫病，最明显的是在艾滋病和心脏移植患者中。该申请解决了开发可以防止潜伏性囊肿重新激活感染的疗法的重大需求。我们之前的研究结果确定了eIF 2 <$（真核起始因子-2）磷酸化在微生物潜伏期中的作用， 这促使我们测试eIF 2去磷酸化抑制剂是否能在体外干扰潜伏的弓形虫感染的再激活。我们发现其中一种药物guanabenz（GA）是一种有效的抗寄生虫药物，也可以抑制体外缓殖子囊肿的再激活。重要的是，GA是一种耐受性良好的FDA批准的药物，可以穿过血脑屏障，这些特性使其成为快速发展的优秀候选药物，成为慢性弓形虫病的创新新疗法。在本申请的R21阶段，我们将在一个充分表征的慢性感染小鼠模型中测试GA的效用，并对GA耐药寄生虫进行筛选，以评估耐药性的可能性和机制。这些突变体将有助于研究这种药物如何抑制寄生虫增殖和感染的再激活。进展到R33期的关键包括证明GA对体内慢性弓形虫的活性或产生GA抗性突变体。如果这些里程碑中的一个或两个都实现，本研究的R33阶段将阐明GA使用互补的生化和遗传方法控制寄生虫复制和潜伏感染的能力的分子机制。

DESCRIPTION (provided by applicant): This application addresses latent chronic infection caused by the protozoan parasite Toxoplasma gondii. In the host, Toxoplasma converts from a proliferative stage (tachyzoite) that causes acute infection to a latent cyst (bradyzoite) stage tht establishes a lifelong chronic infection. Chronic toxoplasmosis is of great clinical importance because the latent infection can reactivate into life-threatening acute toxoplasmosis, most notably in AIDS and heart transplant patients. This application addresses the significant need to develop therapies that can prevent latent cysts from reactivating infection. Our previous findings established a role for eIF2¿ (eukaryotic initiation factor-2) phosphorylation in microbial latency, prompting us to test if inhibitors of eIF2¿ dephosphorylation could interfere with reactivation of latent Toxoplasma infection in vitro. We found that one such drug, guanabenz (GA), is a potent anti-parasitic agent that also inhibits the reactivation of bradyzoite cysts in vitro. Importantly,GA is a well-tolerated FDA-approved drug that crosses the blood-brain barrier, properties that make it an outstanding candidate for rapid advancement as an innovative new treatment for chronic toxoplasmosis. In the R21 phase of this application, we will test the utility of GA in a well-characterized mouse model of chronic infection, and conduct a screen for GA-resistant parasites in order to assess the likelihood and mechanism of drug resistance. These mutants will facilitate studies to define how this drug inhibits parasite proliferation and the reactivatio of infection. Milestones for advancement to the R33 phase include either a demonstration of GA activity against chronic Toxoplasma in vivo or the generation of GA-resistant mutants. If one or both of these milestones are achieved, the R33 phase of this study will elucidate the molecular mechanism underlying the ability of GA to control parasite replication and latent infection using complementary biochemical and genetic approaches.